Past Pot Use May Be Detected In Sweat For Up To Four Weeks, Study Says

Baltimore, MD: The primary psychoactive ingredient in marijuana, THC, may be detectable at low levels in the sweat of daily cannabis users for up to four weeks after they cease using the drug, according to clinical trial data published in the journal Forensic Science International.

Investigators at the National Institute on Drug Abuse (NIDA) assessed the sensitivity of sweat patch technology in 11 daily cannabis users. All of the subjects tested positive for THC during their first week of abstinence, three tested positive for two weeks, and one subject continued to test positive for four weeks after ceasing his use of cannabis.

By contrast, subjects administered daily doses of oral THC did not have a positive sweat patch result.

Sweat patches consist of an absorbed cellulose pad that is applied to the skin with an adhesive and is generally worn by subjects for up to one week. The technology is primarily used in drug treatment and criminal justice settings.

For more information, please contact Paul Armentano, NORML Senior Policy Analyst, at: paul@norml.org. Full text of the study, “Excretion of Delta(9)-tetrahydrocannabinol in sweat,” appears in the May issue of the journal Forensic Science International.